Displays the <th> header cell for a column in the question bank.
Context variables required for this template:
* extraclasses: CSS classes to add to the th. E.g. "questionstatus pr-3".
* help: (optional, may be omitted) help icon. The structure here needs to be as from help_icon::export_for_template().
Other fields vary, depending on whether the column is sortable.
Column with plain title, not sortable:
* sortable: false
* tiptitle: Column name (e.g. "Status")
* sorttip: (optional) must be true if tip is present.
* tip: (optional) a tool tip to show, if the title needs explanation. E.g. "Select questions for bulk actions".
Sortable column, with a single type of sort (e.g. question type)
* sortable: true
* sortlinks: HTML of the title, in a link to sort by this. E.g. "<a href=\"http:\/\/localhost\/moodle_head\/question\/edit.php?courseid=100000&qbs1=-qbank_viewquestiontype%5Cquestion_type_column&qbs2=qbank_viewquestionname%5Cquestion_name_idnumber_tags_column-name\" title=\"Sort by Question type descending\">\n T<i class=\"icon fa fa-sort-asc fa-fw iconsort\" title=\"Ascending\" role=\"img\" aria-label=\"Ascending\"><\/i>\n<\/a>"
Sortable column, with an overall title, and multiple sort types (e.g. question name/idnumber)
* sortable: true
* title: "Question"
* sortlinks: Several sort links concatenated. E.g. "<a href=\"http:\/\/localhost\/moodle_head\/question\/edit.php?courseid=100000&qbs1=qbank_viewquestionname%5Cquestion_name_idnumber_tags_column-name&qbs2=qbank_viewquestiontype%5Cquestion_type_column\" title=\"Sort by Question name ascending\">\n Question name\n<\/a> \/ <a href=\"http:\/\/localhost\/moodle_head\/question\/edit.php?courseid=100000&qbs1=qbank_viewquestionname%5Cquestion_name_idnumber_tags_column-idnumber&qbs2=qbank_viewquestiontype%5Cquestion_type_column&qbs3=qbank_viewquestionname%5Cquestion_name_idnumber_tags_column-name\" title=\"Sort by ID number ascending\">\n ID number\n<\/a>"